JP2001016766A - Power system failure section decision method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a power system failure section decision method which can realize both improvement in failure section decision precision and improvement in verification process speed. SOLUTION: An entire power supply interrupted section whose power supply is interrupted by failure cut-off is generated (Step S1). The entire power supply interruption section is divided by the breakers opened before the failure, the breakers opened after a failure on transmission lines and terminal apparatuses among apparatuses in the entire power supply interruption section to generate estimated object power supply interruption sections (Step S2). The estimated object power supply interruption sections are combined to generate power supply interruption blocks (Step S3). A power supply interruption block combination is generated from the power supply interruption blocks (Step S4). The power supply interruption block is localized to decide on a failure section, and the type of the failure is also decided in matching with the power supply interruption block combination (Step S7).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accident section and equipment at the time of a power system accident at a central power supply command center, a local power supply command center, and a system control station in various power systems using a system control computer or a general-purpose computer. And a method for automatically determining a power system accident section.

[0002]

2. Description of the Related Art In recent years, a method of determining a power system accident section using a knowledge engineering technique represented by an expert system has been developed. The present applicant has also applied for a patent for a method of determining a power system accident section.
50671, JP-A-9-22457, JP-A-10-
The application is published as No. 117431. These methods will be briefly described. FIG. 3 is a model diagram of a first example of a power system accident. A case in which a conventional (disclosed in Japanese Patent Application Laid-Open No. 4-50671) power system fault section determination method is applied to this power system fault will be described.

In the power system shown in FIG. 3, it is assumed that buses A, B, and C of each of the substations A, B, and C are connected by a transmission line AB1L and a transmission line BC1L. These transmission lines AB1L and BC1L
Is connected to a protection relay and a circuit breaker. The protection relay has a function of detecting an accident, and outputs an open command to the circuit breaker when an accident is detected. The circuit breaker performs the opening operation in response to the protection relay opening command, and shuts off the accident section. As a result, the accident section is separated from the healthy section, and the spread of the accident is prevented. Here, the circuit breaker opened after the accident is called an open circuit breaker after the accident. Some circuit breakers are opened before the accident, and such a circuit breaker is called a pre-accident open circuit breaker to distinguish them.

A system control computer or a general-purpose computer (hereinafter simply referred to as a computer) includes, in addition to the above-mentioned protection relays and circuit breakers, all terminal devices (hereinafter, protection relays, circuit breakers, terminal devices) included in a power system. In addition to remotely controlling the state of the device collectively at a remote location (for example, each of the A, B, and C substations), the operation information is obtained by constantly monitoring the operation.

Further, the computer stores in advance a system (including a protection relay and a circuit breaker, which has been opened before the accident), as a system configuration information in a database (not shown) built in or connected to the computer as system configuration information. And grasps the power system before the accident occurred. The operation information and the system configuration information are collectively referred to as system information. Then, when an accident occurs in the power system, the computer detects all facilities that have been out of operation due to the accident.

A first accident example of the power system shown in FIG. 3 will be described. First, an accident occurs in transmission line BC1L, and protection relay B
(Change) Breaker B (change) 02 is shut off in response to the open command issued by 02S. After that, an accident occurs following the transmission line AB1L, and the protection relay A (variable) 01S and the circuit breaker A (variable) 01 and the circuit breaker according to the open command issued by the protection relay B (variable) 01S B (odd) 01 shuts off. The circuit breaker C (variable) 01 is closed even after the accident. The actual protection relay is DZS1 (44S1) which is a short-circuit distance protection relay for B (variable) 02, and PWS (display line protection relay (for short-circuit) for A (variable) 01 and B (variable) 01. 17S) is connected, the protection relay operation as described above is performed.

In the substations A (variant), B (variant) and C (variable), the operation information of the protection relay operation is not detailed information,
It is assumed that only the aggregated relay information of short-circuit (S) relay operation and ground fault (G) relay operation can be obtained. At this time, the short-circuit (S) relay and the ground fault (G) relay have a protection range of ± 4 sections (a transmission line, a bus, and a transformer are defined as one section) and a settling time of 0 section.
It is treated collectively as a 3-second protection relay.

After the occurrence of the accident, the computer generates, based on the system information, a total power outage section which is a set of protection relays, circuit breakers, and equipment that has been outaged due to the accident, based on the accident interruption. In the first accident example shown in FIG.
AB1L, B (variable) bus, and BC1L, C (variable) bus.

Subsequently, a power outage section to be estimated is generated in the entire power outage section. In the first accident example shown in FIG. 3, the circuit is divided by the circuit breaker B (variant) 02, the circuit breaker A (variable) 01, and the circuit breaker B (variable) 01 which actually operated due to the accident. : Estimated blackout section 02: B (variable) bus-Estimated blackout section 03: BC1L, C (variable) bus.

[0010] Then, the divided power failure sections to be estimated are combined to generate a power failure block composed of one or more adjacent / continuous combinations. Specifically,-Power failure block 01: Estimated power outage section 01-Power outage block 02: Estimated power outage area 02-Power outage block 03: Estimated power outage area 03-Power outage block 04: Estimated power outage area 01 + Estimated power outage area 02 -Blackout block 05: Estimated target blackout section 02 + Estimated blackout section 03-Blackout block 06: Estimated blackout section 01 + Estimated blackout section 02 + Estimated blackout section 03. Since the estimation target power outage section 01 and the estimation target power outage section 03 are not adjacent to each other, it goes without saying that a power outage block is not configured. In the power outage blocks 01 to 06, the following inference is made assuming that a simple accident has occurred.

A power failure block combination is generated so as to cover all power failure sections. Such a power failure block combination is as follows. -Power failure block combination 01: power failure block 01 + power failure block 02 + power failure block 03-Power failure block combination 02: power failure block 01 + power failure block 05-Power failure block combination 03: power failure block 04 + power failure block 03-Power failure block combination 04: power failure block 06 . All power outage block combinations are estimated power outage section 01 + estimation power outage section 02 + estimation power outage section 03 when considered in units of estimation power outage. The power outage block combination 01 is a combination assuming a triple accident, the power outage block combination 02 and the power outage block combination 03 are a combination assuming a double accident, and the power outage block combination 04 is a combination assuming a simple accident.

In the following, the power failure block is subdivided from the protection range of the protection relay operated due to the accident to generate an accident candidate section (a section including equipment in which an accident may occur). For each path from this accident candidate section to the terminal of the power failure block, verify the validity of the actual protection relay operation from the relationship between the protection range of the protection relay in the path and the time coordination with the settling time
(Verification of accident candidate section). This process is performed for all the power failure blocks.

[0013] As a result of the verification, an accident candidate section in which the protection relay has a large number of illegal operations (generally, it is impossible that the illegal operation of the relay is more than a certain number (usually two or more) by empirical judgment of the operator). It is judged that there is no accident and is excluded from the accident candidates, and the accident candidate section is narrowed down. Finally, between each power failure block, the conclusion of a simple accident or a multiple accident is derived by combining accident candidate sections where an accident still remains.

In Japanese Patent Application Laid-Open No. 9-222457, for example, results of judgment and evaluation by a transmission line fault point locating device such as a customer premises accident judging device, a substation premises accident judging device, a fault locator, etc. There is disclosed an invention in which an actual accident point is confirmed using an operation result of an automatic recovery device such as a final shutoff after an automatic reclosing and an accident confirmed section is generated. By using this accident confirmed section, the number of accident candidate sections that are candidates for accident points can be reduced, and the inference accuracy is improved.

Further, when there are a plurality of fault-determined sections in one power failure block, the assumption of the power failure block (assuming one unit in which a simple accident occurs) is inconsistent, and the assumption of the power failure block is incorrect. Therefore, the power failure block combinations using the power failure blocks are deleted, and the remaining power failure block combinations are used, thereby improving the accuracy of determining simple accidents and multiple accidents.

[0016]

SUMMARY OF THE INVENTION In the conventional method,
The operation information on the protection relay is not detailed information that specifies the type of relay, namely the main protection relay and the back-up protection relay.It generally has a protection range of several sections in the ± direction (transmission line and bus direction), This is the aggregated relay information expressed as a protection relay that performs a short-circuit relay operation.

When handling the aggregated relay information, as described above, since the protection range of the protection relay extends over a wide range of ± direction, it can be estimated that an accident may occur in the ± direction of the protection relay operated by the accident. There is a possibility that an accident may occur in the ± direction of the circuit breaker operated by the accident, and the entire blackout section was divided into the estimated blackout section using all the circuit breakers operated by the accident.

In this case, the entire power failure section is divided into small power failure sections to be estimated, and the power failure block and the power failure block combination are also finely divided. There is a disadvantage that the number of accident candidate sections increases due to the fine power failure block, and the verification processing speed of the accident candidate sections decreases. In addition, there is a disadvantage that a plurality of simple accident and multiple accident results are generated as final accident section and accident type judgment results due to the fine power failure block combination. Therefore,
SUMMARY OF THE INVENTION It is an object of the present invention to provide a power system fault section determination method that achieves both improvement in fault section determination accuracy and improvement in verification processing speed.

[0019]

According to a first aspect of the present invention, there is provided an electric power system accident section determining method, comprising the steps of: In a power system accident section determination method for determining an accident section having the facility based on system information including operation information of a protection relay and a circuit breaker connected to the power system configuration information and the like, the power supply based on the system information Generate a total power outage section that is a set of equipment that has been powered down due to accident interruption in the system, and the open-circuit breaker before accident in which the open / close state before the accident is `` open '' among the equipment included in the entire power outage section, Among the circuit breakers operated by the transmission line protection relay having both the transmission line direction and the busbar direction as the protection range, the circuit breaker opened after the accident at the transmission end of the transmission line, and the terminal device are selected, and the circuit breaker before the accident is selected. The entire power outage section is separated by the post-open circuit breaker and the terminal device to generate the power outage section to be estimated, and the power outage section to be estimated is one section, or the power outage section to be estimated is two or more adjacent continuous sections. A power outage block which is a combination of the power outage blocks, a power outage block combination combined so as to cover all the power outage sections from the power outage blocks, the power outage blocks are localized, an accident section is determined, and the power outage block combination is generated. It is characterized in that the judgment is made in accordance with the accident type of simple accident or multiple accidents.

[0020] Among the circuit breakers operated by the protection relay whose protection range protects both the direction of the transmission line and the direction of the bus, among the circuit breakers operated after the accident at the transmission end of the transmission line, only the circuit breaker to be estimated is generated, After the accident at the receiving end of the transmission line, the open circuit breaker was not used. In this way, even when the aggregated relay information is used, unnecessary segmentation of the power outage section to be estimated can be prevented.

According to the method for determining an accident section of a power system according to the second aspect, in the method for determining an accident section of a power system according to the first aspect, an accident occurs in a power outage block which is the estimation target power outage section of one section. The section where the points are confirmed is regarded as an accident-determined section, and when there are a plurality of accident-determined sections in the power outage block, an accident-determined section combination is generated, the accident section is determined from the accident-determined section, and the accident-determined section is determined. It is characterized in that the accident type of multiple accidents is determined from the combination.

For example, a judgment result and an evaluation result by a transmission line fault point locating device such as a customer premises accident judging device, a substation yard accident judging device, a fault locator, etc., or an automatic recovery such as a final cut-off after automatic re-closing of a transmission line. The actual accident point is confirmed using the operation result of the device, and an accident confirmed section is generated. Depending on the power system accident, it may be confirmed that a plurality of accidents have actually occurred in one power interruption block that is assumed to have caused a simple accident due to the enlargement of the power interruption block. Even in such a case, the inference accuracy is improved using the actual accident determination section.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for determining a power system fault section according to an embodiment of the present invention will be described. FIG. 1 is a flowchart illustrating a flow of a determination process of a power system accident section determination method, FIG. 2 is an explanatory diagram illustrating an entire power failure section, and FIG. 3 is a model diagram of a first example of a power system accident. . In order to explain the present embodiment, the power system fault section determination method of the present embodiment is applied to the first fault example used in the description of the related art,
Clarify differences. In addition, the description which overlaps with the prior art is omitted.

As shown in FIG. 1, the flow of the determination process of the power system fault section determination method is as follows: Step S1: Generate all power outage sections; Step S2: Generate target power outage section; Step S3: Generate power outage block; Step S4: Step S5: determination of an accident-determined section, step S6: determination of multiple accidents by combining accident-determined sections, step S7: determination of an accident section and an accident type.

Next, the processing in each step will be described. (1) Step S1: Generation of all blackout sections A set of equipment that has lost power due to accident interruption is obtained, and all blackout sections are generated. FIG. 2 shows an example of all power outage sections in the power system. As shown in FIG. 2, the power system is divided into a total power failure section due to an accident, a healthy section, and a power failure section before the accident where the power has stopped before the accident. These sections are separated by an open circuit breaker before an accident, an open circuit breaker after an accident, a terminal device, and the like. In this way, it is assumed that the entire blackout section of FIG. 3 described above is generated.

In the first accident example, as in the prior art, an accident occurs in the transmission line BC1L, the breaker B (variation) 02 is cut off by the protection relay B (variation) 02S, and then the transmission line AB1L is connected to the transmission line AB1L. When an accident occurs, protection relay A (variable) 01S and protection relay B (variable) 0
This is an example in which the circuit breaker A (variable) 01 and the circuit breaker B (variable) 01 are interrupted by 1S. The circuit breaker C (variable) 01 is closed even after the accident.

In the case of A (variable), B (variant), and C (variant), the operation information of the operation relay can obtain only aggregated relay information such as a short-circuit (S) relay operation and a ground fault (G) relay operation. At this time,
Short-circuit (S) relays and ground fault (G) relays have a protection range of ± 4 sections (the transmission line, bus, and transformer are defined as one section), and a settling time of 0.3 sec. Are dealing.

After the occurrence of the accident, based on the system information, a total power interruption section, which is a set of protection relays, circuit breakers, and equipment that has been shut down due to the accident, is generated. In the power system shown in Fig. 3, ・ All blackout sections: AB1L, B (variable) bus, BC1L, C (variable) bus.

(2) Step S2: Generation of Estimated Power Failure Section Subsequently, the sections are separated using the post-accident open circuit breaker, the pre-accident open circuit breaker, and the terminal equipment included in the entire power failure section, and the estimation target power failure is performed. Generate an interval. Here, the post-accident open circuit breaker is not a conventional open circuit breaker, but a circuit breaker operated by a transmission line protection relay that protects both the transmission line direction and the bus direction. However, only the post-accident open circuit breaker at the transmission end of the transmission line is excluded, and the post-accident open circuit breaker at the transmission end of the transmission line is excluded. The reason for this is to prevent segmentation of the power outage section to be estimated and simplify subsequent processing.

The entire blackout section is divided by the circuit breaker A (variable) 01 and the circuit breaker B (variable) 02 selected so as to satisfy the above-mentioned rules, and the estimated blackout section is generated. The B (variation) 01 is not a target for the separation of the estimated power interruption section because it is an open circuit breaker after the accident at the power transmission end at the transmission line receiving end where the protection direction is ± by the protection relay B (variation) 01S. Each estimated power outage section divided by circuit breaker A (variable) 01 and circuit breaker B (variable) 02 is as follows:-Estimated power outage section 01: AB1L, B (variable) bus-Estimated power outage section 02: BC1L, C (F) The bus.

(3) Step S3: Power Outage Block Generation One or more continuous estimation target power outage sections are connected to generate a power outage block. It is assumed that a power failure block is one unit in which a simple accident occurs. When a power failure block is generated from the example of FIG. -Blackout block 01: Estimated blackout section 01-Blackout block 02: Estimated blackout section 02-Blackout block 03: Estimated blackout section 01 + Estimated blackout section 02 A simple accident has occurred in these blackout blocks 01 to 03. And proceed with the following inference.

(4) Step S4: Power Outage Block Combination Generation A power outage block combination is generated so as to cover all estimation target power outage sections. -Power failure block combination 01: Power failure block 01 + power failure block 02-Power failure block combination 02: Power failure block 03 In the above example, the power failure block combination 01 is a combination assuming a double accident. The power outage block combination 02 is a combination assuming a simple accident.

(5) Step S5: Judgment of Accident Confirmation Section (6) Step S6: Judgment of Multiple Accidents by Combination of Accident Decision Sections Step S5 is information other than the aggregated relay information and can be reliably used for an accident that has actually occurred. It is a step of detecting the determined detailed information from other equipment in the power system and determining a section in which the location of the accident and the type of the accident are determined, and step S uses such an accident-determined section. This is a step of determining simple / multiple accidents. In this accident example, it is determined that such determined information could not be detected, and the process jumps to step S7.

(7) Step S7: Judgment of the Accident Section and the Accident Type Based on the protection range of the protection relay operated by the accident, the power failure block is separated to select an accident candidate section (a section including equipment in which an accident may have occurred). Generate.

For each path from the accident candidate section to the end of the power failure block, the validity of the actual protection relay operation is verified from the relationship between the protection range of the protection relay in the path and the settling time period (accident candidate section verification). I do. As a result of the verification, an accident candidate section where the protection relay has many irregular operations (generally, the number of illegal operations of the relay
(Usually two or more) cannot be considered), it is determined that there is no accident, and is excluded from accident candidates, and the accident candidate section is narrowed down.

The processing relating to step S7 is performed for the power failure block 01 and the power failure block 02 in the case of the power failure block combination 01, and is performed for the power failure block 03 in the case of the power failure block combination 02. Finally, the conclusion of a simple accident or multiple accidents is derived from the combination of accident candidate sections where the possibility of an accident still remains.

In this way, the number of power failure blocks generated in the same power system accident is reduced to three in the present embodiment, compared to the conventional six blocks, and the verification work later is easy and quick. Also, in the past, the assumed accident types were large, such as triple accidents, double accidents, and simple accidents, but according to the present embodiment, the assumed number of accidents was double accidents and simple accidents. And the subsequent verification work is easier and faster.

Next, a case where the present embodiment is applied to another power system accident will be described. FIG. 4 is a model diagram of a second example of a power system accident. Note that FIG. 1 is referred to for the description of the determination processing. In the second accident example shown in FIG. 4, in a double accident of transmission lines AB1L and AB2L, protection relay A (variable) 0
1S, B (variable) 01S, A (variable) 02S, B (variable) 02S
(Variation) 01, B (Variation) 01, A (Variation) 02, and B (Variation) 02 are examples in which the accident was interrupted. Actually, A (variable) and B (variable) display line protection relay
(It is assumed that the PWS (17S) relay (for short circuit) has been activated).

In A (variable), B (variable) and C (variable), the operation information of the operation relay can only obtain aggregated relay information such as short-circuit (S) relay operation and ground fault (G) relay operation. . At this time, the short-circuit (S) relay and the ground fault (G) relay are treated as relays with a protection range of ± 4 sections (transmission line, bus, and transformer as one section), and a settling time of 0.3 seconds. . In addition, the transmission line AB1L and
AB2L accident has been confirmed.

Next, the processing in each step will be described. Note that the description of the processing overlapping with the processing described above will be simplified. (1) Step S1: Generation of all blackout sections After the occurrence of the accident, based on the system information, a total blackout section that is a set of protection relays, circuit breakers, and equipment that has been shut down due to the accident is created based on the system interruption. I do. In the power system shown in FIG. 4, the total power outage section is: AB1L, AB2L, B (variable) bus, BC1L, BC2L, C (variable) bus.

(2) Step S2: Generation of Estimated Power Failure Section Subsequently, the sections are divided using the post-accident open circuit breaker, pre-accident open circuit breaker, and terminal equipment included in the entire power failure section, and the estimation target power failure is performed. Generate an interval. In this case, the post-accident open circuit breaker is a post-accident open circuit breaker operated by a transmission line protection relay having a protection range in both the transmission line direction and the busbar direction. Open circuit breakers only, excluding open circuit breakers after an accident at the receiving end of the transmission line.

In the example of FIG. 4, only the post-accident open circuit breakers A (variable) 01 and A (variable) 02 can be used to generate the power failure section to be estimated, and the sections cannot be divided. The estimated target blackout section is substantially as follows.・ Estimated blackout section 01: AB1L, AB2L, B (variable) bus, BC1
L, BC2L, C (variable) bus

(3) Step S3: Generation of Power Outage Block One or more continuous power outage blocks to be estimated are connected to generate a power outage block. However, there is only one power outage area to be estimated, and the power system accident shown in FIG. The power outage block is as follows. -Power failure block 01: Power failure section 01 to be estimated

(4) Step S4: Power Outage Block Combination Generation A power outage block combination is generated so as to cover all estimated power outage sections. However, there is only one power outage block, and the power outage block combinations are as follows. Become. -Power failure block combination 01: Power failure block combination 01 The power failure block combination 01 is a combination assuming a simple accident.

(5) Step S5: Judgment of Accident Confirmed Section For example, judgment / evaluation results by a transmission line fault point locating device such as a customer premises accident judging device, a substation accident judging device, and a fault locator, or a transmission The actual accident point is confirmed using the operation result of the automatic restoration device such as the final interruption after the automatic re-closure of the electric wire, and the accident confirmed section is generated. In the example of the power system accident shown in FIG. 4, an accident has been confirmed in AB1L and AB2L, and AB1L and AB2L are accident-determined sections. As a result, the power failure block 01 has two accident confirmed sections.

(6) Step S6: Multi-accident determination by combining accident-determined sections If there are a plurality of accident-determined sections in a power failure block generated only from one estimated power failure section, multiple accidents are determined by combining them. It is determined that there is. In the case of the power system accident shown in FIG. 4, it is determined that the accident type in the accident sections AB1L and AB2L is a double accident.

(7) Step S7: Judgment of the Accident Section and the Accident Type Since the accident section and the accident type have already been determined, the process ends without judging the accident section and the accident type using the power failure block.

In the conventional power system accident determination method, since the power outage section to be estimated is finely divided, it is unlikely that a plurality of accident confirmed sections exist in the power outage block where a simple accident is assumed to occur. If there is more than one accident confirmed section within the block, the assumption of the power outage block will be inconsistent, so there is no accident in this power outage block,
It was determined to be a healthy section. Therefore, as in the case of the second accident in FIG. 4, when only one power outage block (one estimation target power outage section) originally exists in the entire power outage section and there are a plurality of accident confirmed sections in that section, the conclusion is made. Could not be derived. However, according to the present embodiment, an actual accident is also detected, and the inference accuracy is improved by using the actual accident confirmed section.

[0049]

According to the present invention, the number of power failure blocks to be generated is reduced, so that the number of generation of an accident candidate section is reduced, and the verification time of the accident candidate section is also reduced. In addition, the number of power failure block combinations to be generated is reduced, and finally, the generation of unnecessary accident types such as double accidents and triple accidents is suppressed. Further, since the actual accident point is detected and included in the determination processing, the determination accuracy is improved. As described above, according to the present invention, it is possible to provide a power system fault section determination method that realizes both an improvement in verification processing speed and an improvement in fault section determination accuracy.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating a flow of a determination process according to an embodiment of a method for determining a power system accident section.

FIG. 2 is an explanatory diagram illustrating an entire blackout section.

FIG. 3 is a model diagram of a first example of a power system accident.

FIG. 4 is a model diagram of a second example of a power system accident.

Claims (2)

[Claims] When an accident occurs in a facility constituting a power system, the facility is controlled based on system information including operation information of a protection relay and a circuit breaker connected to the power system, power system configuration information, and the like. In the power system accident section determination method for determining an accident section having, in the power system based on the system information, to generate a total power outage section that is a set of equipment that is outage due to accident shutdown in the power system, in the total power outage section Among the included facilities, the pre-accident open circuit breaker whose open / close state before the accident is "open", and the transmission line among the circuit breakers operated by the transmission line protection relay that has the protection range in both the transmission line direction and the bus direction The post-accident open circuit breaker and terminal equipment at the transmitting end are selected, and the pre-accident open circuit breaker, post-accident open circuit breaker, and terminal equipment are used to divide the entire blackout section to generate the estimated blackout section. A power outage block that is a combination of the estimated power outage section between the estimated power outage sections or two or more adjacent continuous power outage sections is generated, and the power outage block is combined so as to cover all power outage sections from the power outage block. A method for determining a power system fault section, comprising: generating a power failure block combination; localizing the power failure block to determine an accident section; and determining from the power failure block combination an accident type such as a simple accident or a multiple accident. 2. The power system accident section determination method according to claim 1, wherein a section in which an accident point is confirmed in a power outage block which is the estimated target power outage section in one section is defined as an accident confirmed section, In the case where a plurality of accident confirmed sections are present, an accident confirmed section combination is generated, and the accident section is determined from the accident confirmed section and the accident type of multiple accidents is also determined from the accident confirmed section combination. Power system accident section determination method.